Dye sublimation inks have long been used for printing on polyester-based materials and objects. Conventionally, sublimation printing processes have used thermal printers and dye transfer paper and have employed analog printing methods. The dye sublimation inks include a pigment suspended in a liquid solvent, such as water. Inkjet inks and inkjet printers have also recently been used for sublimation printing processes.
The market for digital textile printing has grown substantially in recent years. This has led to increased usage of and interest in solvent-based, e.g. water-based, dye sublimation inks. Outside of textile applications, other polyester-based materials are also decorated using dye sublimation technology. Examples include films, containers, packaging, and materials having a polyester coating, such as wood or metal.
Two types of printing processes can be used in sublimation printing. Direct printing requires that ink is jetted directly onto a substrate, cured, and then thermally treated such that the dye diffuses from the ink into the substrate. Indirect printing requires that ink is printed onto heat-resistant transfer paper or another transfer material and cured, e.g. via UV radiation. The transfer paper is placed over a substrate and heat is applied that causes the dye to transfer to the substrate from the transfer paper and form an image.
Indirect printing is both more costly and more complex due to the presence of the transfer paper. Moreover, the transferring process can be materially hindered if the image is not printed onto a flat substrate.
While direct printing eliminates the need for transfer paper, problems arise related to the removal of residual ink that remains on the surface of the substrate following sublimation. If the substrate is flat and durable, it is possible to manually scrape the residual ink from the imaged substrate. However, the scraping process is difficult to effectively automate. In some instances, scraping may not be practical or possible. For example, if the substrate is soft or has surface flatness variability, it can be very difficult to remove residual ink.